Does anyone have any feedback on how well these work?
Any problems with using them?
Any good reviews?

 

Yes, work fine.

 

Why would there be any problems using them?

 

I switched from NGK Platinium to Denso Irdium. The reason I went with Denso is that the electrode is at .04 mm compared to .7 mm that of the NGK Iridium. The smaller the electrode the better the arc is, and less power to make spark. Go to Denso's site www.densoaftermarket.com I think they compare plugs. Didn't notice a big difference but car runs alittle bit smoother and fuel mileage increased a very slight amount.

 

I have had no problems with them so far. Really helps from having mass amounts of carbon on my old plugs.

 

Recently switched from Denso Iridium to NGK Iridium. The butt dyno says they seem to be just fine.

I may have noticed a slight dip in fuel economy though. Not sure... I need to take care of some other things before I can be certain.